Chapter 26. Exercises for Chapter 8

Exercise 8.1: Simple EJB QL Statements

The exercises in this section reveal some of the basic aspects of EJB QL programming and functionality. You’ll explore basic finder methods, ejbSelect methods, and the use of the IN operation in EJB QL queries.

Start Up JBoss

If you already have JBoss running, there is no reason to restart it.

Build and Deploy the Example Programs

Perform the following steps:

  1. Open a command prompt or shell terminal and change to the ex08_1 directory created by the extraction process

  2. Set the JAVA_HOME and JBOSS_HOME environment variables to point to where your JDK and JBoss 4.0 are installed. Examples:

    Windows:C:workbookex08_1> set JAVA_HOME=C:jdk1.4.2 C:workbookex08_1> set JBOSS_HOME=C:jboss-4.0
    Unix:$ export JAVA_HOME=/usr/local/jdk1.4.2 $ export JBOSS_HOME=/usr/local/jboss-4.0

  3. Add ant to your execution path.

    Windows:C:workbookex08_1> set PATH=..antin;%PATH%
    Unix:$ export PATH=../ant/bin:$PATH

  4. Perform the build by typing ant.

As in the last exercise, you will see titan.jar rebuilt, copied to the JBoss deploy directory, and redeployed by the application server.

Examine the JBoss-Specific Files

This exercise introduces no new features in JBoss-specific files. If you think you need to, review Exercise 6.1 of this workbook to understand the JBoss-specific files in this example.

Initialize the Database

The database tables for this exercise will automatically be created in JBoss’s default database, HypersonicSQL, when the EJB JAR is deployed. To initialize all the tables in this example, though, you must perform the Ant task run.initialize:

C:workbookex08_1>ant run.initialize
Buildfile: build.xml

prepare:

compile:

run.initialize:
   [java] added Bill Burke
   [java] added Sacha Labourey
   [java] added Marc Fleury
   [java] added Jane Swift
   [java] added Nomar Garciaparra

As in the preceding exercise, all business logic is implemented within a stateless session bean. If you would like to see the database initialization code, take a look at com.titan.test.Test81Bean’s initialize( ) method, which creates all the entity beans for this exercise.

Examine and Run the Client Applications

Each example method of Test81Bean implements the example code fragments shown in the EJB book. Each Test81Bean method is invoked by a small, simple client application.

Client_81a

The Client_81a program demonstrates a few simple finder methods that are exposed through the Customer home interface:

public interface CustomerHomeLocal extends javax.ejb.EJBLocalHome 
{
   ...
   public CustomerLocal findByName(String lastName, 
                                String firstName)
      throws FinderException;

   public Collection findByGoodCredit( )
      throws FinderException;
   ...
}

The Customer EJB’s deployment descriptor defines these finder methods as follows:

<query>
   <query-method>
      <method-name>findByName</method-name>
      <method-params>
        <method-param>java.lang.String</method-param>
        <method-param>java.lang.String</method-param>
      </method-params>
    </query-method>
    <ejb-ql>
        SELECT OBJECT(c) FROM Customer c
        WHERE c.lastName = ?1 AND c.firstName = ?2
    </ejb-ql>
</query>
<query>
   <query-method>
      <method-name>findByGoodCredit</method-name>
      <method-params/>
    </query-method>
    <ejb-ql>
        SELECT OBJECT(c) FROM Customer c
        WHERE c.hasGoodCredit = TRUE
    </ejb-ql>
</query>

The example also demonstrates a few ejbSelect methods, defined in the Address EJB’s deployment descriptor as follows:

<query>
   <query-method>
      <method-name>ejbSelectZipCodes</method-name>
      <method-params>
        <method-param>java.lang.String</method-param>
      </method-params>
    </query-method>
    <ejb-ql>
        SELECT a.zip FROM Address AS a
        WHERE a.state = ?1
    </ejb-ql>
</query>
<query>
   <query-method>
      <method-name>ejbSelectAll</method-name>
      <method-params/>
    </query-method>
    <ejb-ql>
        SELECT OBJECT(a) FROM Address AS a
    </ejb-ql>
</query>
<query>
   <query-method>
      <method-name>ejbSelectCustomer</method-name>
      <method-params>
        <method-param>com.titan.address.AddressLocal</method-param>
      </method-params>
    </query-method>
    <ejb-ql>
        SELECT OBJECT(C) FROM Customer AS c
        WHERE c.homeAddress = ?1
    </ejb-ql>
</query>

Because ejbSelect methods are private to the entity bean class, the Address home interface needs custom home methods to wrap and invoke the private ejbSelect methods.

public interface AddressHomeLocal extends javax.ejb.EJBLocalHome 
{  
   ...
   public Collection queryZipCodes(String state)
      throws FinderException;

   public Collection queryAll( )
      throws FinderException;

   public CustomerLocal queryCustomer(AddressLocal addr)
      throws FinderException;
}

These custom home methods need corresponding ejbHome methods defined in the Address bean class. All they do is delegate to the ejbSelect methods they wrap.

public abstract class AddressBean implements javax.ejb.EntityBean 
{
   ...
   public abstract Collection ejbSelectZipCodes(String state)
      throws FinderException;

   public abstract Collection ejbSelectAll( )
      throws FinderException;

   public abstract CustomerLocal ejbSelectCustomer
      (AddressLocal addr)
      throws FinderException;

   public Collection ejbHomeQueryZipCodes(String state)
      throws FinderException
   {
      return ejbSelectZipCodes(state);
   }

   public Collection ejbHomeQueryAll
                     ( )
      throws FinderException
   {
      return ejbSelectAll( );
   }

   public CustomerLocal ejbHomeQueryCustomer(AddressLocal addr)
      throws FinderException
   {
      return ejbSelectCustomer(addr);
   }
   ...
}

Custom home methods are described briefly in Chapter 5 of the EJB book and in more detail in Chapter 11. As you can see, they are extremely useful in exposing private ejbSelect methods so that they can be invoked by test programs or business logic. All the workbook example programs for Chapter 8 use the custom home methods for this purpose.

Client_81a invokes these queries and displays their output. To run it, invoke the Ant task run.client_81a. Remember to set your JBOSS_HOME and PATH environment variables. The output should look something like this:

C:workbookex08_1>ant run.client_81a
Buildfile: build.xml

prepare:

compile:

run.client_81a:
     [java] FIND METHODS
     [java] --------------------------------
     [java] SELECT OBJECT(c) FROM Customer c
     [java] WHERE c.lastName = ?1 AND c.firstName = ?2
     [java] Find Bill Burke using findByName
     [java]    Found Bill Burke
     [java]
     [java] SELECT OBJECT(c) FROM Customer c
     [java] WHERE c.hasGoodCredit = TRUE
     [java] Find all with good credit.  Sacha has bad credit!
     [java]    Bill has good credit.
     [java]    Marc has good credit.
     [java]    Jane has good credit.
     [java]    Nomar has good credit.
     [java]
     [java] SELECT METHODS
     [java] --------------------------------
     [java] SELECT a.zip FROM Address AS a
     [java] WHERE a.state = ?1
     [java] show ejbSelectZipCodes with queryZipCodes
     [java]    01821
     [java]    02115
     [java]    02116
     [java]
     [java] SELECT OBJECT(a) FROM Address AS a
     [java] show ejbSelectAll with queryAll
     [java]    123 Boston Road
     [java]    Billerica, MA 01821
     [java]
     [java]    Etwa Schweitzer Strasse
     [java]    Neuchatel, Switzerland 07711
     [java]
     [java]    Somewhere Dr.
     [java]    Atlanta, GA 06660
     [java]
     [java]    1 Beacon Street
     [java]    Boston, MA 02115
     [java]
     [java]    1 Yawkey Way
     [java]    Boston, MA 02116
     [java]
     [java]    West Broad Street
     [java]    Richmond, VA 23233
     [java]
     [java]    Somewhere
     [java]    Atlanta, GA 06660
     [java]
     [java]
     [java] SELECT OBJECT(C) FROM Customer AS c
     [java] WHERE c.homeAddress = ?1
     [java] show ejbSelectCustomer using Bill's address.
     [java] The customer is:
     [java]    Bill Burke
     [java]    123 Boston Road
     [java]    Billerica, MA 01821

Client_81b

The Client_81b program gives you a chance to investigate some of the queries illustrated in the EJB book. For an explanation of the details of the tested queries below, please refer to Section 8.3.2 in Chapter 8 of the EJB section of this book. The business logic for this example is implemented in com.titan.test.Test81Bean, in the test81b( ) method.

All the EJB QL queries in this example are ejbSelect methods. Again, these ejbSelect methods are wrapped by custom home methods. This example tests the following Customer EJB QL queries and home methods:

query:

SELECT c.lastName FROM Customer AS c

ejbSelect method:

ejbSelectLastNames( )

custom home method:

queryLastNames( )

ejbHome method:

ejbHomeQueryLastNames( )

query:

SELECT c.creditCard FROM Customer c

ejbSelect method:

ejbSelectCreditCards( )

custom home method:

queryCreditCards( )

ejbHome method:

ejbHomeQueryCreditCards( )

query:

SELECT c.homeAddress.city FROM Customer c

ejbSelect method:

ejbSelectCities( )

custom home method:

queryCities( )

ejbHome method:

ejbHomeQueryCities( )

query:

SELECT c.creditCard.creditCompany.address

FROM Customer AS c

ejbSelect method:

ejbSelectCreditCompanyAddresses( )

custom home method:

queryCreditCompanyAddresses( )

ejbHome method:

ejbHomeQueryCreditCompanyAddresses( )

query:

SELECT c.creditCard.creditCompany.address.city

FROM Customer AS c

ejbSelect method:

ejbSelectCreditCompanyCities( )

custom home method:

queryCreditCompanyCities( )

ejbHome method:

ejbHomeQueryCreditCompanyCities( )

Client_81b invokes these queries and displays their output. To run it, invoke the Ant task run.client_81b. Remember to set your JBOSS_HOME and PATH environment variables. The output should look something like this:

C:workbookex08_1>ant run.client_81b
Buildfile: build.xml

prepare:

compile:

run.client_81b:
     [java] SIMPLE QUERIES with PATHS
     [java] --------------------------------
     [java] SELECT c.lastName FROM Customer AS c
     [java]    Burke
     [java]    Labourey
     [java]    Fleury
     [java]    Swift
     [java]    Garciaparra
     [java]
     [java] SELECT c.creditCard FROM Customer c
     [java]    5324 9393 1010 2929
     [java]    5311 5000 1011 2333
     [java]    5310 5131 7711 2663
     [java]    5810 5881 7788 2688
     [java]    5450 5441 7448 2644
     [java]
     [java] SELECT c.homeAddress.city FROM Customer c
     [java]    Billerica
     [java]    Neuchatel
     [java]    Atlanta
     [java]    Boston
     [java]    Boston
     [java]
     [java] SELECT c.creditCard.creditCompany.address
     [java] FROM Customer AS c
     [java]    West Broad Street
     [java]    Richmond, VA 23233
     [java]
     [java]    West Broad Street
     [java]    Richmond, VA 23233
     [java]
     [java]    West Broad Street
     [java]    Richmond, VA 23233
     [java]
     [java]    Somewhere
     [java]    Atlanta, GA 06660
     [java]
     [java]    Somewhere
     [java]    Atlanta, GA 06660
     [java]
     [java]
     [java] SELECT c.creditCard.creditCompany.address.city
     [java] FROM Customer AS c
     [java]    Richmond
     [java]    Richmond
     [java]    Richmond
     [java]    Atlanta
     [java]    Atlanta

Client_81c

The Client_81c program lets you investigate some more queries illustrated in the EJB book. For an explanation of the details of the tested queries below, please refer to Section 8.3.3 in Chapter 8 of the EJB section. The business logic for this example is implemented in com.titan.test.Test81Bean, in the test81c( ) method.

All the EJB QL queries in this example are ejbSelect methods. Again, these ejbSelect methods are wrapped by custom home methods. This example tests the following Customer EJB QL queries and home methods:

query:

SELECT OBJECT( r )

FROM Customer AS c, IN( c.reservations ) AS r

ejbSelect method:

ejbSelectReservations( )

custom home method:

queryReservations( )

ejbHome method:

ejbHomeQueryReservations( )

query:

SELECT r.cruise

FROM Customer AS c, IN( c.reservations ) AS r

ejbSelect method:

ejbSelectCruises( )

custom home method:

queryCruises( )

ejbHome method:

ejbHomeQueryCruises( )

query:

SELECT cbn.ship

FROM Customer AS c, IN( c.reservations ) AS r,

IN( r.cabins ) AS cbn

ejbSelect method:

ejbSelectShips( )

custom home method:

queryShips( )

ejbHome method:

ejbHomeQueryShips( )

Client_81c invokes these queries and displays their output. To run it, invoke the Ant task run.client_81c. Remember to set your JBOSS_HOME and PATH environment variables. The output should look something like this:

C:workbookex08_1>ant run.client_81c
Buildfile: build.xml

prepare:

compile:

run.client_81c:
     [java] THE IN OPERATOR
     [java] --------------------------------
     [java] SELECT OBJECT( r )
     [java] FROM Customer AS c, IN( c.reservations ) AS r
     [java]    Reservation for Alaskan Cruise
     [java]    Reservation for Alaskan Cruise
     [java]    Reservation for Atlantic Cruise
     [java]    Reservation for Atlantic Cruise
     [java]    Reservation for Alaskan Cruise
     [java]
     [java] SELECT r.cruise
     [java] FROM Customer AS c, IN( c.reservations ) AS r
     [java]    Cruise Alaskan Cruise
     [java]    Cruise Alaskan Cruise
     [java]    Cruise Atlantic Cruise
     [java]    Cruise Atlantic Cruise
     [java]    Cruise Alaskan Cruise
     [java]
     [java] SELECT cbn.ship
     [java] FROM Customer AS c, IN( c.reservations ) AS r,
     [java] IN( r.cabins ) AS cbn
     [java]    Ship Queen Mary
     [java]    Ship Queen Mary
     [java]    Ship Queen Mary
     [java]    Ship Queen Mary
     [java]    Ship Titanic
     [java]    Ship Titanic
     [java]    Ship Titanic
     [java]    Ship Titanic
     [java]    Ship Titanic
     [java]    Ship Titanic
     [java]    Ship Queen Mary
     [java]    Ship Queen Mary
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